Recording of electrical impulses



G. L. DIMMICK RECORDING 0F`ELECTRICAL IMPULSES Dec. 26, 1939.

2 Sheets-Sheet l Filed June 25, 1938 Gtfotneg Dec. 26, 1939. G. l..DIMMlcK 2,184,548

RECORDING 0F ELECTRICAL IMPULSES Filed June 25, 1938 2 Sheets-Sheet 2 igF595 %f47 y Ig/1%' ,60

/l=,j=r/` v 4 l 4a F595 F592- @f0- Suventor Patented Dec. 26, 1939RECDRDING OF ELECTRICAL R'IPULSES Glenn L. DimmickyHaddoneld, N. J.,assigner to Radio Corporation of America, a corporation of DelawareApplication June 25, 1938, Serial No. 215,910

1.0 Claims.

This invention relates to the recoiding of electrical impulses such asthose of audio frequency, and has for its principal object the provisionof an improved recording apparatus and method of operation wherebyovershooting of adjacent records one onto the path of the other isavoided'and the operation of such apparatus is simplified and improved.This application is in part a continuation of my application Serial No.181,593, iiled December 24, 1937.

The invention is Amore particularly adapted to the recording of pluraltrack records such as those of the double-hump type, the push-pull typeand the like. OneN of its distinguishing characteristics is theutilization of a pair of differently polarized light beams which areenlarged as the signal modulation increases. These beams are separatedby an opaque area which is decreased in size as the signal modulationincreases and which altogether disappears at extremely high signalmodulation or overshooting. Although the use of polarized light ispreferred, I may accomplish substantially the same result by using anappropriately complementary color screen.

In a preferred form of the invention, the dilTerently polarized lightbeams are moved outwardly from the center of the record track inresponse to increase in the signal modulation and Vice versa. Since theopaque area intermediate the adjacent records forms the inner edge ofthe adjacent record tracks and this opaque area is obliterated atovershooting or extremely high modulation, interference of one trackwith the other is altogether avoided.

of each beam to a separate area of the light slit` and preventinginterference of the adjacent record track areas.

The polarizing material utilized to produce these various effects may beof any suitable form such, for example, as the commercial productcommonly known as polaroid.

The invention will be better understood from the following descriptionconsidered in connection with the accompanyingr drawings and its scopeis indicated by the accompanying claims.

Referring to the drawings',

Figure 1 illustrates a system including a preferred form of theinvention,

Figures 2, 3, 6 and 7 are fragmentary drawings illustrating theessential features of modified forms of the invention,

Figures l and 5 are explanatory diagrams relating to the distinction ofthe inventionpver somewhat similar prior art systems,

Figure-8 is al type of class A push-pull recordY produced by thearrangement of Figs. 6 and 7,

Figure 9 is a double hump reccrd'produced by a recording system of thetype illustrated by, Fig.

l, and

Figure l() is a similar type of class A push-pull record produced by thearrangement of Fig. 3.

lThe recording'sys'tem of Figgl includes a pick.- up device ormicrophone l' from which the impulses to be recorded are suppliedthrough ampliers ll and. l2- to the operating coil I3 of a re. cordinggalvanometer i4. Light from a source l5 is projected through a lens i6,the triangularly shaped aperture of an aperture plate il', a pair oidiierently polarized movable varies i3 and i9 and lenses 20 and 2i tothe `mirror of the galvanometer lll.

The differently polarized kvanes lll and i9v are movable transversely ofthe aperture of the plate ll and are illustrated as overlapping at theiradjacent ends. The extent to which they overlap is determined by theircontrol mechanism which is energized in accordance with the envelopecurrent or volume of the recorded impulses. To this end, a component ofthe recorded impulses isv supplied through a rectifier and lter network22 to an operating coil 23 which acts through a lever "24 and aresilient member 25 to move the vane supporting arms 26 and 2l inresponse toy change in the volume or amplitude of the recorded impulses.It will be observed that the lever 24 is pivoted at 2S and' is biased bymeans of a spring 2l which opposes the pull of the coil 23 on the lever.Under these conditions the vanes i8 and I9 are moved transversely of theaperture of the plate ll in accordance with the signal level. The lightbeams have their contour outlined by the noncverlapping areas 23 and 29,which vary in size in accordance with the signallevel. f

The differently polarized beams dened by the areas 28 and'ES 'areapplied to the mirror of the galvanometer llt and from this mirror arereflected to the recording surface 3B through the lens 2l, the lightslit of a plate 3l and lenses 32 and 33. The images of these dilierentlypolarized light beamsare indicated at- 365 and 35 on the light slitplate 3l. Since the spacing between these images is determined by theoverlapped or opaque area of the vanes i3 and l 9, and this overlappedarea is dependent on the level of the re.- corded impulses, it will beapparent `thatovershooting of the beams in a manner to cause in` iii .terference between the adjacent record tracks is avoided. The resultingtype of record is shown in Fig. 9 wherein the two component records areindicated at 36 and 3l and the shading produced by the intermediateopaque area is indicated at 38. It will be observed that when the vanes|8 and I9 are moved outwardly to a point where they do not overlap, theintermediate opaque area 38 ceases to exist and the extension of one ofthe 10,l component records into the track normally oc- 50 accordancewith the volume or envelope of the recorded impulses. With thisarrangement, the overlapped central area of the light slit is opaque andthe width of this area is increased and decreased longitudinally of theslit so as to variably shade the central part of the record in pullrecord illustrated by Fig. 10.

of the light slit of the plate 3|.

the manner previously explained in connection with Fig. 9.

Fig. 3 illustrates a similar modification of a recorder suitable forproducing the class A push- As in the lmodification of Fig. 2, the lightbeams 4|J and 4| are overlapped at their adjacent ends and are vibratedlongitudinally of the light slit in n accordance with the volume of thesignal to be recorded. The recording beam itself, however, is in theform of a trapezcid having its ends displaced With respect to oneanother. The operation of this modication of the invention will beapparent in View of the previous explanation. Thus, at relatively lowmodulation of the recorded impulses the differently polarized beams 40-and 4| are overlapped to a comparatively great extent and the centralopaque portion 42 of the record is comparatively wide. At relal' tivelyhigh modulation of the impulses, however,

this central opaque area 44 decreases in width and finally disappears atextremely high modulation which would otherwise produce interferencebetween the adjacent record tracks 45 and 46.

Diierent prior art arrangements for recording a class A push-pull recordare illustrated by Figs. 4 and 5. Thus, in Fig. 4, a light beam of theshape indicated at 4'| is vibrated transversely It will be observed thatthe opposed ends of this beam are offset to prevent interference betweenthe different record tracks. The type of record produced by thisarrangement is indicated by the central area 48 of the record of Fig. 8.In the somewhat similar arrangement of Fig. 5, a pair of similarlyshaped light beams 49 and 50 are vibrated transversely of the light slitof the plate 3|. This arrangement, of course, results *in a negativesound record which is the reverse of that produced by the arrangement ofFig. 4. In the arrangement of Figs. 6 and '7, a pair of rectangularlight beams 50 and 5| are vibrated longitudinally of the light slit ofthe plate 3| to produce a record such as that shown by Fig. 8. In thismodification, the light slit has associated with its opposite halvesdifferently polarized materials as indicated at 42 and 43 of Fig. '7,the light slit part 42, for example,

5 being associated with the similarly polarized beam 50 and the lightslit part 43 being associated with the similarly polarized beam 5|. Atovershooting the polarized beams pass beyond the center of the slit and,of course, their light is excluded by the diierently polarized lightslit section and interference of the records, one with the other, isthereby prevented as indicated in the record of Fig. 8.

In any of the above-described species of the invention, I may substitutea color lter for one of the polarizing screens and a complementary colorfilter for the other of said screens, the exact relation of the colorschosen depending upon the characteristics of the film which is to beused. For use with panchromatic film, I may use one filter of orange redand the other filter of grennish blue, while, for film sensitivity inthe blue and near ultra violet regions only, I may use one lter which istransparent to the near ultra violet and not to the blue, and anotherfilter which is transparent to the blue but opaque to the ultra violetand other combinations of filters that may be chosen according to theparticular characteristics of the film. The filter, however, shouldpreferably transmit light having approximately equal actinic effect uponthe lm so that the respective film areas will be exposed to the samedegree. For instance, with an ortho type of film, if one filter has ahigh transmission in the blue, the band of transmission of this ltershould be relatively narrow or its density should be relatively high,while the complementary filter should transmit as much of the spectrumas possible due to the lower sensitivity of the film to the otherregions of the spectrum.

I claim as my invention:

1. An electrical impulse recorder including means for producing aplurality of light beams, means for diierently polarizing said beams,means for modulating said beams in accordance with the impulses to berecorded, and means for varying the areas of said beams in accordancewith the level of said impulses.

2. An electrical impulse recorder including means for producing aplurality of light beams, means including a pair of vanes movable inopposite directions for diierently polarizing said beams, means formodulating said beams in accordance with the impulses to be recorded,and means for moving said vanes in accordance with the level of saidimpulses.

3. The combination of means for dening a light beam, means including apair of partially overlapped vanes for converting said light beam to apair of differently polarized light beams, means for modulating saidpair of light beams in accordance with the impulses to be recorded, andmeans for varying the overlapping of said vanes in accordance with thelevel of said impulses.

4. An electrical impulse recorder including means for producing aplurality of differently polarized light beams, light slit meansdiierently polarized as at its opposite ends, and means for vibratingsaid polarized beams transversely of said slit means in accordance withthe impulses to be recorded.

5. The electrical impulse recording method which includes producing aplurality of differently polarized light beams, modulating said beams inaccordance with the impulses to be recorded, and varying they size ofsaid beams in accordance with said impulses.

6. An electrical impulse recorder including means for producing aplurality of light beams.

means including a pair of vanes movable in opposite directions eachtransparent to light of a characteristic to which the other is opaque,means for modulating said beams in accordance with the impulses to berecorded, and means for moving said vanes in accordance With the levelof said impulses.

'7. The combination of means for defining a light beam, means includinga pair of partially overlapped vanes for converting said light beam to apair of light beams having diierent characteristics, each Vane beingopaque to light havingthe characteristics transmitted by the other vane,means for modulating said pair of light beams in accordance with theimpulses to be recorded, and means for varying the overlappingA of saidvaries in accordance with the level of said impulses. y

8. An electrical impulse recorder including means for producing aplurality of light beams having diierent characteristics, light slitmeans having means at its opposite ends transparent to light of one ofsaid characteristics and opaque to light of the other of saidcharacteristics, and means for Vibrating said beams transversely of saidslit means in accordance with the impulses to be recorded.

9. An electrical impulse recorder including means for producing aplurality of light beams, means including a pair of complementary colorvaries movable in opposite directions for differently coloring saidbeams, means for modulating said beams in accordance with the impulsesto be recorded, and means for moving said vanes in accordance with thelevel of said impulses'.

10. The combination of means for deiining a light beam, means includinga pair of partially overlapped vanes for converting said light beamv Cil

